Nutrition research publications can be maddening. Their amount is overwhelming, but once the poorly conducted studies are filtered out, once those that may have some statistical but not clinical significance are filtered out, you get rid of those making grandiose claims about health effects based on questionnaires that were delivered on one occasion. If you eliminate those that overinterpret results based on too few subjects, exclude those that imply long-term effects based on short-term trials, and ignore studies that unrealistically extrapolate data from animals to humans, you don't have much to do. But let's snack on studies on the current topic of "wellness", i.e. "time-limited eating". The thesis is that our state of health depends not only on what we eat, but also when we eat it.
While there's certainly controversy over the details, there's general agreement on the "what". A diet should be primarily based on vegetables, fruits and whole grains, with a minimum of processed foods, especially those high in sugar and salt. Fish is preferred to other meat products and extra virgin olive oil is preferred to refined seed oils. Saturated fats, like butter and red meat, should be limited, as should foods that are seared by high heat. Alcohol at most a couple of times a week and soft drinks as close as possible. Now let's get to the "when".
In 1935, nutritionist Dr. Cornell University's Clive McCay found that mice fed a diet that reduced caloric intake by 30% were more physically active and much less prone to senile diseases than their free-grazing lab peers. They also lived 40% longer! The interpretation at the time was that the benefits were due to reduced production of tissue-damaging “reactive oxygen species (ROS),” which are by-products of the reaction between glucose and oxygen, the reaction that produces energy needed for vital processes in cells. Chemically, ROS are "free radicals," electron-deficient species ready to steal electrons from any molecule they can find. Because electrons are the “glue” that holds atoms together in molecules, their loss leads to bond rupture. If the affected molecules are proteins or nucleic acids, it can lead to disease or accelerated aging. But when there is less food to metabolize, the argument goes, fewer free radicals are produced, leading to longer lifespans.
Since McCay's original observation, numerous studies in fruit flies, mice, dogs, and monkeys have shown that calorie restriction increases longevity. However, reduced free radical formation may not be the only factor involved. In early experiments with rodents, it was not recognized that the animals consumed their limited amount of food within hours of feeding, meaning they had long periods of fasting.
In a normal state, cells "burn" glucose provided by food to produce the energy needed to sustain life. Fasting without glucose supply activates a backup system. Instead of "burning" glucose, cells begin to metabolize stored fats. In the process, fats are broken down into acetone, acetoacetate, and beta-hydroxybutyrate, called "ketone bodies," which serve as an alternative fuel for energy production. But "ketosis", as this fat burning process is called, is also a signal to the body that no food is coming, a crisis situation. The "metabolic switch" to burn ketones instead of glucose triggers a series of cellular responses aimed at survival. Cells begin to produce various molecules that repair DNA, reduce inflammation, regulate glucose sensitivity, and break down damaged cells (autophagy). All of these processes can benefit health.
This raises the question of whether the observed benefits of a calorie-restricted diet in animals are a function not only of the reduced calorie content, but also of the time that no food is consumed. Is there an ideal way, the researchers wondered, to incorporate fasting into an eating plan? What if, instead of just cutting calories, when you were eating, you were mindful of the foods that make up this calorie-restricted diet? This is how the concept of “time-restricted eating” or its alternative name “intermittent fasting” came about.
Several schemes have been proposed. Eat a normal diet for 5 days and reduce calories to 500-700 two days a week (5:2 fasting), do the same every other day of the week (4:3 fasting) or fast Tested 14-16 hours a day (time limited daily feeding). In the latter case, there are no calorie restrictions during the 8-10 hours that the food is consumed, but experiments have shown that this automatically leads to a reduction in calories as there is no late-night snacking. While most studies involving these therapies have resulted in weight loss, the benefits, such as improved glucose regulation, blood pressure, inflammation, and loss of abdominal fat, go beyond what one would expect from weight loss. For example, in one study, women were assigned either a 5:2 intermittent fasting or a 25% calorie-restricted daily diet. Over 6 months, both groups lost the same amount of weight, but the 5:2 group had improved insulin sensitivity and a greater reduction in waist circumference.
Other studies related to intermittent fasting have shown increased running endurance, improvements in HDL/LDL cholesterol ratio, decreased free radical activity, and reduced markers of systemic inflammation. Some preliminary studies have also shown suppression of tumor growth in various types of cancer. In animal models, second-day fasting may slow the onset and progression of neurological diseases such as Alzheimer's, Parkinson's, and multiple sclerosis. There is even evidence that intermittent fasting can improve memory and cognitive performance.
Evidence of benefit continues to mount. In one much-cited study, a group of mice were only allowed access to food for a 9-hour period, while mice in the control group were allowed to eat whenever they wanted. In the end, the two groups ate roughly the same amount of food, so the results obtained cannot be attributed to differences in calorie intake, at least in this case. After 7 weeks, tissue samples were taken from various organs and examined for changes in gene expression. Genes code for the production of proteins, so the researchers basically measured whether the production of different proteins increased or decreased. It showed that genes coding for inflammatory proteins were less active, while genes that make proteins that repair DNA damage and those that inhibit cancer cell survival were turned on. But of course rats are neither male nor female.
So what about men or women? An interesting study examined changes in various proteins produced by eating alone for 10 hours and fasting for 14 hours. The subjects, 8 men and 6 women, all observed the Muslim religious month of Ramadan, during which there is no eating or drinking between sunrise and sunset. They were specifically chosen because they each met at least three criteria for "metabolic syndrome," defined as central obesity, insulin resistance, high blood pressure, high triglyceride levels, and high cholesterol. These parameters are easy to monitor and can provide insight into the health effects of fasting, as well as changes in gene expression.
All of the markers of metabolic syndrome changed in the right direction during the 14-hour month of fasting, as did proteins involved in cancer cell killing, DNA repair, and improving immune function. All very interesting, but the experimental group was small and the study duration of one month was short. In addition, all subjects had metabolic syndrome and caloric intake was not accounted for. Basically, not much can be concluded about the general population.
However, that's not the case in a study that compared the effects of early and late eating on glucose levels, insulin production, triglyceride levels, and fatty acid oxidation, which is a measure of ketosis. Participants ate dinner at 6 or 10 p.m. and then had their blood chemistry checked hourly through an intravenous line. Late dinner resulted in increased glucose intolerance and decreased fatty acid oxidation, both of which may promote obesity. Why should this happen? Metabolism usually slows down during sleep because the body uses less energy. Therefore, ingested glucose and fat are not burned for energy, but are stored as fat. If dinner is prepared earlier, the metabolism stays active until bedtime and stores less fat. This study seems to support the benefits of limited daily fasting because if no food is eaten after late afternoon, the reduced metabolism associated with sleep is less of a problem since most foods are metabolized in 5 or 6 hours. between the last meal and bedtime.
Now that I was ready to end with a final plaudit of intermittent fasting, I came across two recently published articles in reputable peer-reviewed journals. It was found that in adults over 40, a gap of less than 4.5 hours between meals, essentially time-restricted eating, was associated with premature death! hell again! The second study asked participants to use an app to record the time of their meals and then correlate it to their body weight as documented in their medical records over a 10-year period. Weight changes were not associated with the time between the first and last meal, which seems to argue against trying to time-limit weight loss.
Where is all this taking us? As is the case with almost every aspect of nutrition, there are controversies and studies to support each side. Separating the wheat from the chaff is challenging and requires a thorough review of studies to try to understand the preponderance of evidence. At this point, this evidence points to calorie restriction as a factor in reducing markers of disease and longevity, but to make recommendations, especially those that are difficult to establish, we need more than just markers. We need long-term human studies with a significant number of subjects that compare normal eating, low-calorie eating, and intermittent fasting with the endpoints of disease or death. These time-consuming tests are difficult, if not impossible, to fund, organize and monitor. In his absence, we're limited to making educated guesses.
Since neither calorie restriction diet has demonstrated any risk, there doesn't seem anything wrong with trying one or the other, whether for weight loss or simply better health and maybe longer life. But I suspect most people can't handle calorie restrictions long-term. It is a pleasure to eat. However, having an early dinner and then fasting until bedtime can be a challenge that can be overcome and is worth trying. At least until the next study comes out that tells us that life expectancy in Spain, where people traditionally eat late, is higher than in North America.
Obviously, the field of nutritional research is very fertile and there are many crops to harvest, but we have to be careful with weeds.
FAQs
Is it important to eat on time why or why not? ›
In general, scheduling what and when you eat will help you maintain a balanced diet and create a more stable energy source, as your metabolism will be engaged at optimal levels all day long. The goal is to eat every 3 to 4 hours in order to keep your blood sugar consistent and for your stomach to optimally digest.
How do I know if I'm eating too much or not enough? ›A telltale sign of overeating is bloating, feeling uncomfortable or even painfully full, according to Taub-Dix. You may even notice your clothing (temporarily) feels tighter after a big meal. Eating to the point of discomfort can often be the result of eating too quickly or while distracted, she said.
What happens when we do not eat enough or eat the right amount of food? ›Typical signs that you're not eating enough can include losing weight, feeling tired, getting ill more often, hair loss, or skin problems. In time, menstrual irregularities and depression may occur. Children may not grow as expected.
What do you think the effect of not eating on time? ›Skipping meals: Causes the body to lower its metabolism (how much energy it needs to function) Causes us to burn less energy (fewer calories) Can lead us to gain weight when we eat our usual amount of food Leaves us with little energy because the body has run out of the fuel we get from food Leaves us sluggish and ...
What is the most important time to eat? ›Breakfast is often described as the most important meal of the day, providing as it does sustenance and energy (i.e., calories) for whatever activities lay ahead. As nutritionist Adelle Davis famously put it back in the 1960s: “Eat breakfast like a king, lunch like a prince and dinner like a pauper.” (Sifferlin, 2013).
Why is it important to eat regularly? ›A well-balanced diet provides all of the: energy you need to keep active throughout the day. nutrients you need for growth and repair, helping you to stay strong and healthy and help to prevent diet-related illness, such as some cancers.
Can eating too little cause weight gain? ›Eating too few calories can be the start of a vicious cycle that causes diet distress. When you cut your calories so low that your metabolism slows and you stop losing weight, you probably will become frustrated that your efforts are not paying off. This can lead you to overeat and ultimately gain weight.
Which is worse overeating or undereating? ›Research shows that being underweight is MORE harmful to your body than being overweight. If you're not eating enough energy, you're literally starving yourself. If you're severely under eating, your body functions will eventually start to shut down and it will likely lead to serious health complications.
How much should I be eating per day? ›Adult females need anywhere from 1,600 to 2,400 calories a day and adult males need anywhere from 2,000 to 3,000 calories a day, according to the USDA's latest “Dietary Guidelines for Americans” report released in 2020.
What happens when you eat a little too much? ›So, what happens to your body when you overeat? Overeating causes the stomach to expand beyond its normal size to adjust to the large amount of food. The expanded stomach pushes against other organs, making you uncomfortable. This discomfort can take the form of feeling tired, sluggish or drowsy.
Is not eating enough worse than eating too much? ›
Remember, eating too little is just as unhealthy as eating too much. Find the right amount of food intake that works best for you, and don't be afraid to experiment with eating more if your health isn't where you want it to be!
What happens if you only eat one meal a day? ›Eating one meal a day can increase your blood pressure and cholesterol. This occurred in a group of healthy adults who switched to one meal a day to participate in a study. If you already have concerns in either area, eating just once a day might not be safe. Eating one meal late can cause your blood sugar to spike.
Does not eating late make a difference? ›“We found that eating four hours later makes a significant difference for our hunger levels, the way we burn calories after we eat, and the way we store fat.”
What are the mental effects of not eating enough? ›Mood is badly affected by under-eating. Under eaters generally feel depressed, low, and prone to be easily irritated or enraged. Panic attacks are a very common side-effect of undereating and are only likely to subside when you recover back to a healthier body weight.
Why is it important to eat slowly? ›Eating slowly can increase fullness hormones
Eating too quickly often leads to overeating, as your brain doesn't have enough time to receive fullness signals. Additionally, eating slowly has been shown to decrease the amount of food consumed during the meal due to an increase in fullness hormones ( 8 , 9 , 10 ).
As a guideline, you should stop eating two to three hours before bed. This will give your body enough time to digest your food, lowering your chances of acid reflux and digestive issues keeping you up.
What are the 3 best times to eat? ›- 6:00 to 9:45 a.m. This is the best time for breakfast. ...
- 10 a.m. Snacktime. ...
- 1 p.m. Lunch break. ...
- 6 p.m. Dinnertime.
The best time to have breakfast is within two hours of getting up. "The sooner you eat breakfast after you wake up, the better it is for your metabolism," says Larson. If you hit the gym in the AM, it's best to have a light meal like a banana or an avocado toast 20-30 minutes before workout.
Does timing of meals matter? ›Timing our meals this way may lead to better body weight, hormone regulation, blood sugar and cholesterol levels, sleep patterns and other metabolic improvements. The evidence indicates that our bodies do best when we eat more in the morning than at night, a pattern that's vastly different from how most Americans eat.
What is the most important thing about eating? ›Eating a healthy, balanced diet is one of the most important things you can do to protect your health. In fact, up to 80% of premature heart disease and stroke can be prevented through your life choices and habits, such as eating a healthy diet and being physically active.
How long should it take to eat a meal? ›
Your meal should take about 20 to 30 minutes. If you're gobbling up your food in 5 to 10 minutes, you're likely to experience indigestion and risk overeating. While you don't need to chew each bite 50 times, try taking a breath or putting down your utensil between bites to help slow your eating down even more.
Do you poop less if you eat less? ›Infrequent bowel movements may be related to inadequate calorie intake. This isn't surprising, since consuming very little food will result in less waste in your digestive tract.
Does your stomach shrink when you starve? ›Myth or Fact: If you cut down on your food intake, you'll eventually shrink your stomach so you won't be as hungry. Answer: Myth. Once you are an adult, your stomach pretty much remains the same size -- unless you have surgery to intentionally make it smaller.
Does Undereating make you skinny? ›THE BOTTOM LINE. Chronically undereating won't help you lose weight, and can often yield the opposite effect as well as lead to nutritional deficiencies. In my experience as a dietitian, having a targeted number on the scale isn't the best way to achieve weight loss or overall health.
Is eating less than 1500 calories good? ›1,500 calories per day would be considered a low caloric intake for most people and would generally not be recommended for the long term.
What is the number 1 healthiest food in the world? ›Lemons. Lemons have been widely regarded in the health industry as the world's healthiest food. The sour fruit is an alkalising powerfood; they have strong anti-inflammatory qualities and can even help to inhibit the growth of cancer cells.
How many calories should I eat a day by age? ›| Gender | Age (years)a | Actived |
|---|---|---|
| Child | 2-3 | 1,000-1,400 |
| Female | 4-8 9-13 14-18 19-30 31-50 51+ | 1,400-1,800 1,800-2,200 2,400 2,400 2,200 2,200 |
| Male | 4-8 9-13 14-18 19-30 31-50 51+ | 1,600-2,000 2,000-2,600 2,800-3,200 3,000 2,800-3,000 2,400-2,800 |
The recommended dietary allowance to prevent deficiency for an average sedentary adult is 0.8 grams per kilogram of body weight. For example, a person who weighs 165 pounds, or 75 kilograms, should consume 60 grams of protein per day.
Is it better to eat little or a lot? ›There are no health benefits to eating more often. It doesn't increase the number of calories burned or help you lose weight. Eating more often also doesn't improve blood sugar control. If anything, eating fewer meals is healthier.
What happens when your stomach is full? ›A stretched, or full, stomach sends signals to the brain that you are full. Eating too much can cause the stomach to stretch past its normal capacity, leading to feeling overly full. This can lead to pressure and discomfort as the contents of the stomach pass into the small intestine.
What happens if you don't eat all day? ›
After eight hours without eating, your body will begin to use stored fats for energy. Your body will continue to use stored fat to create energy throughout the remainder of your 24-hour fast. Fasts that last longer than 24 hours may lead to your body to start converting stored proteins into energy.
Do you live longer if you eat less? ›Eating fewer calories may slow down aging and increase longevity. Eating less may lengthen your life. Researchers have increased life-spans in yeast and mice by having them consume fewer calories per day, and ongoing studies suggest that a strict low-calorie diet may slow aging in primates, too.
Does eating less make you healthier? ›Science has shown for years that restricting the number of calories ingested while maintaining overall nutrition is a health-promoting lifestyle habit. It is associated with lower blood pressure and blood lipid levels, for one thing.
Is it OK to only eat two meal a day? ›Based on research that shows eating two meals won't necessarily get you all the nutrients you need, though, I do recommend choosing three medium-size meals between 400 and 600 calories, plus one to three snacks at 150 to 200 calories per day for optimal nutrition and satiety.
Why am I not hungry after not eating all day? ›Mental health conditions, like anxiety, depression, and stress, can all have a negative effect on hunger levels. Other physical conditions, such as pregnancy, hypothyroidism, and more, can also cause a decrease in appetite.
Why am I gaining weight when I'm eating less and working out? ›You've gained muscle.
And here's an often overlooked fact: Muscle tissue is more dense than fat tissue. So as you gain more muscle and lose fat, you change your overall body composition, which can result in a higher weight, but a smaller figure and better health.
Some of your body's functions run on autopilot. That includes burning calories. No matter whether we stay up all night or fall asleep at the dinner table, our bodies have an internal schedule that says to burn the most calories in the late afternoon and early evening and the least in the early morning.
Does eating after 9pm cause weight gain? ›The Bottom Line. Physiologically, calories don't count for more at night. You won't gain weight by merely eating later if you eat within your daily calorie needs. Still, studies show that nighttime eaters typically make poorer food choices and eat more calories, which can lead to weight gain.
What are the advantages of eating late? ›While eating before bed may not be the best idea for some people, it can benefit others — it may actually curb nighttime eating and aid weight loss. Some evidence suggests that, rather than causing weight gain, eating a bedtime snack may help some people lose weight.
What are 3 consequences of not eating well? ›In the short term, poor nutrition can contribute to stress, tiredness and our capacity to work, and over time, it can contribute to the risk of developing some illnesses and other health problems such as: being overweight or obese. tooth decay. high blood pressure.
How do you know if you're in starvation mode? ›
On starvation mode, just as the name suggests, you are constantly hungry, even after eating. Not only does your diet not allocate enough food to help keep you full, but worse your food cravings during this time tend to increase.
Should you drink water while eating? ›There's no concern that water thins down or weakens down (dilute) the digestive juices or interfere with digestion. In fact, drinking water during or after a meal helps how your body breaks down and processes food (digestion).
What does eating slow say about you? ›Your eating habits may reveal how you approach life
Specifically, slow eaters generally like to be in control and know how to appreciate life. Fast eaters tend to be ambitious, goal-oriented, open to new experiences, and often impatient.
One common piece of advice is to chew your food an estimated 32 times before swallowing. It takes fewer chews to break down soft and water-filled food. The goal of chewing is to break down your food so it loses texture. Chewing 32 times appears to be an average number applied to most bites of food.
What is the meaning of eating time? ›: the usual time for serving a meal.
Why is it important to eat within an hour of waking? ›The idea behind eating within the first hour of waking for blood sugar and hormonal imbalances is that your body is primed and ready to receive nutrients at that time—it's been a while since you last ate, after all—and balancing both out from the jump can lead to an uptick in energy.
How long should it take you to eat? ›Stretch out your meals
“People should take more than 20 minutes to eat a meal — ideally about 30 minutes — so that you can have an opportunity for your brain to catch up with your stomach,” Dr. Heinberg says. If you're working toward weight loss and weight management, here are some strategies Dr.
Your meal should take about 20 to 30 minutes. If you're gobbling up your food in 5 to 10 minutes, you're likely to experience indigestion and risk overeating. While you don't need to chew each bite 50 times, try taking a breath or putting down your utensil between bites to help slow your eating down even more.
What happens if you eat too fast? ›Leisurely eating is better for your health, especially when it comes to digestion, weight and nutrition. When you eat too fast, you swallow more air, which can cause bloating and gas. Slowing down to properly chew your food helps to break down larger particles of food into smaller ones, aiding digestion.
What happens when you eat on time? ›03/6Boosts metabolism
The time at which you eat your food also determines your metabolism. When we get up in the morning, our metabolism is at its highest. If you do not fuel your body at this time, your body will not be able to sustain the metabolic rate.
When should you eat time? ›
How Often Should You Eat Tuna? Tuna is incredibly nutritious and packed with protein, healthy fats and vitamins — but it should not be consumed every day. The FDA recommends that adults eat 3–5 ounces (85–140 grams) of fish 2–3 times a week to get enough omega-3 fatty acids and other beneficial nutrients ( 10 ).
How soon after you wake up should you eat? ›The best time to have breakfast is within two hours of getting up. "The sooner you eat breakfast after you wake up, the better it is for your metabolism," says Larson. If you hit the gym in the AM, it's best to have a light meal like a banana or an avocado toast 20-30 minutes before workout.
What is the first thing you should eat in the morning? ›A balanced breakfast typically includes protein, fiber, and produce. If you're looking to build a healthy morning meal, try easy options like eggs, whole wheat toast with toppings, nuts, and green tea. Breakfast is a great way to start your day.
What should I eat immediately after waking up? ›- Avocado. Avocados are loaded with vitamins, minerals, and healthy fats that give our body energy that will last for hours. ...
- Watermelon. Even minor dehydration can cause you to wake up not feeling your best. ...
- Almonds. ...
- Kale. ...
- Bee pollen. ...
- Banana. ...
- Spinach. ...
- Dates.